Heat exchange agitator



March M, 1958 F, M, YOUNG HEAT EXCHANGE AGITATOR Filed Jan; 9, 1956ATTORNE 1.

2,826,220 HEAT EXCHKNGEhfififibh l redlVI. Young, Racinmwis assignor toYoung Radiator Company, Racine, Wis., a corporationof WisconsinAspartame-Mar s,1'956,seaaiivu'ssaosz 4 Claims. (Cl. 138 -38) Thisinvention relates to turbulence or agitator" strips for the tubes offluid heat exchangers, particularly those used for cooling the oilrequired in high-powered, highheat producing engines.

It is well known that in tubular heat exchangers the tendencytoward theequalization of temperature between the fluidflowing through the tubesand the fluid e'nvfelopthe tubes takes place through Qthe tube wall.here the fluid i's flowing through the tu e under pressure it is alsowell known that the column at 'fluid in eifect comprises a concentricseries of films or laminae, from the .United States Patentv ice core tothe circumference coincident with the inner face of the tube wall. Underpressure these concentric films or laminae tend to move successivelyslower from the core outwardly to the circumference where the film orlamina in frictional contact with the inner face of the tube wall movesthe slowest; in fact, tends almost to immobility. Obviously, therefore,under such conditions the heat dissipation of the films or laminae offluid is successively less from the circumference inwardly to the core,where the heat dissipation is at a very minimum. To overcome thisdecreasing heat dissipation, from the wall of the tube inwardly to thecore of the fluid column, it has been a common practice to incorporatein the tubes some kind of fin, baflle, or turbulence strip. These aredesigned to slice or break-up and radially deflect these concentricfluid films or laminae so as to effect contact of all the fluidmolecules with the heat-dissipating tube wall. The construction of suchdevices has followed a myriad of patterns in an attempt to get areasonably high-temperature drop with a minimum pressure drop.

With the advent of increasingy high-powered, high-heatcreating engines,particularly for use in modern transport and military equipment, theheat exchange producers have been confronted with the demand for heatexchangers requiring less and less space yet capable of achieving anacceptable cooling of the coolant flowing through the tubes. This hasforced the heat exchange manufacturers to reduce the size and increasethe number of tubes they put into a heat exchanger. Such smaller unitshave necessitated the use of higher pressures in an attempt to attainthe requisite temperature drop. On occasion, these tubes have been assmall as outside diameter. Clearly, any attempt to use internalagitators requires a very narrow and thin strip. This presents newproblems in the design and form of effective agitator elements.

The main objects of this invention, therefore, are to provide animproved form of internal agitator especially for the smaller diametertubes of heat exchangers; to provide an improved form of agitator ofthis kind capable of achieving a most practical high-temperature dropwithout too great a build-up in pressure; and to provide an agitatorstrip of this kind which is so simple to manufacture and insert into thetubes, as to make its production extremely economical.

In the accompanying drawings:

Fig. 1 is a perspective view of a strip of material which 2,826,220Patented Mar. 11, 1. 958

modification.

Thedi'stinctiveconceptofthis invention involves a s'trip, usually verythin and narrow, with a staggered arrangement of arcu ate shaped-lobesvariously struck out from the opposite faces 'of the'strip andonopposite sides of the longitudinal medial line.

The herein shown ag'ita't 'or, femb'ody'ing this concept,

com rises a theta-1 strip *5 oft-his, narrow width from which'are struckout thelob'e'sli. For sometypes of heat "exchangers, the strip may haveto be as thin as 0:017 inch and narrow enough to be inserted into a tubeof /1 'outside'diaineter.

As so clearly "show "in the drawings, the cuts'which form the arcuateperusus oftlie tones 6 have radiithe axes of which are located in themedian l'irie'of the stri 5. Thus theatres of th'e's'eloues s tue inacircumference embracing the bppos'i'te iedg'es of the s'trip 5. Thediameter of such a circumference is just enough less than the insidediameter of the tube 10 to permit the agitator to slip into the tubewith these arcuate peripheries of the lobes 6 practically in contactwith the inside wall of the tube (see Fig. 3) Moreover, the arc of eachlobe is materially greater than degrees (see Fig. 3) so that theimmediately successive lobes on opposite edges overlap the longitudinalmedian line of the strip 5. This overlap, at the peripheries of thelobes, is substantially onequarter of the tube diameter. Suchoverlapping of the lobes insures a breakup of the laminar flow along theaxis of the tube wherein these agitators are used.

The straight edges, which otherwise define the lobes 6, are here shownto be disposed at right angles to each other and are substantiallyparallel and normal respectively to the median line of the strip 5.

The cuts which form the lobes 6, may be variously arranged and the lobesvariously struck out from the face of the strip 5. As shown in all ofthe figures except Fig. 5, the lobes 6 are arranged in pairs eachsuccessive pair along the strip being located on opposite sides of themedian line. The lobes 6 of each pair are struck out from opposite facesof the strip, with the next adjacent lobes of successive pairson theopposite side of the medial line-struck out from the opposite faces ofthe strip. As shown in Fig. 5, each successive lobe 6 is cut out onopposite sides of the medial line. Moreover, such successive lobe isstruck out from opposite faces of the strip.

Striking out of the lobes 6 forms an opening 9 adjacent each lobe. Thestrip 5 is inserted into the tube 10 so that the openings 9 are on theadvancing side of the oil flow through the tubes. Thus, when such anagitator, as that herein shown, is in use, these lobes 6 and adjacentopenings 9 are constantly breaking up the oil flow, causing the oil, inits traverse of the tube, to be deflected first from one side of thestrip and then from the other as well as radially of the tube. This willmaterially reduce, if not entirely eliminate, the normal tendency towardlaminar oil flow through the tubes not so equipped.

Variations and modifications in the details of structure and arrangementof the parts may be resorted to within the spirit and coverage of theappended claims.

I claim:

1. An agitator for tubular heat exchangers comprising a strip havingarcuate-shaped lobes struck out transversely from the opposite lateraledges thereof, the arc of each lobe being more than 90 degrees of acircle the periphery of which circle substantially embraces the oppositelateral edges of the strip, the axis of which circle is in the medianline of the strip, the other edge of each lobe being straight anddisposed transversely to the plane of the strip, the lobes struck outalong opposite edges of the strip overlapping each other along theirstraight edges longitudinally of the strip, which overlap at theperipheries of the lobes is substantially equal to one quarter of thewidth of the strip.

2. An agitator for tubular heat exchangers comprising a strip havingarcuate-shaped lobes struck out transversely from the opposite lateraledges thereof, the arc of each lobe being more than 90 degrees of acircle the periphery of which circle substantially embraces the oppositelateral edges of the strip, the axis of which circle is in the medianline of the strip, the other edge of each lobe being straight andright-angularly disposed to the plane of the strip, the lobes struck outalong one edge of the strip overlapping the lobes struck out along theother edge of the strip a distance substantially equal to one quarter ofthe width of the strip with the straight edges of the lobes parallel.

3. An agitator for tubular heat exchangers comprising a strip havingsuccessive pairs of arcuate-shaped lobes struck out alternately alongopposite lateral edges of the strip, the arc of each lobe being morethan 90 degrees of a circle the periphery of which circle substantiallyembraces the opposite lateral edges of the strip, the axis of whichcircle is in the median line of the strip, the other edge of each lobebeing straight and disposed transversely to the plane of the strip, thepairs of lobes struck out along the opposite edges of the stripoverlapping each other along their straight edges longitudinally of thestrip, which overlap at the peripheries of the lobes is substantiallyequal to one quarter of the width of the strip.

4. An agitator for tubular heat exchangers comprising a. strip havingsuccessive pairs of arcuate-shaped lobes struck out alternately alongopposite lateral edges of the strip, the arc of each lobe being morethan degrees of a circle the periphery of which circle substantiallyembraces the opposite lateral edges of the strip, the axis of whichcircle is in the median line of the strip, the other edge of each lobebeing straight and right-angularly disposed to the plane of the strip,the pairs of lobes struck out along one edge of the strip overlappingthe lobes struck out along the other edge of the strip a distancesubstantially equal to one quarter the width of the strip with thestraight edge of the lobes parallel.

References Cited in the file of this patent UNITED STATES PATENTS515,974 Schwaerer Mar. 6, 1894 2,677,394 Brinen et a1. May 4, 19542,688,986 OBrien Sept. 14, 1954 FOREIGN PATENTS 680,070 Germany July 27,1938

